1. Field of the Invention
The present invention generally relates to an end point detecting method of metal etching and device thereof, and more particularly to an end point detecting method of metal etching and device thereof, capable of eliminating the effect of the set up location for the scanner of the end point detecting device of metal etching and judging the etching end point time of the metal film more precisely.
2. Description of Prior Art
Please refer to FIG. 1, which shows a diagram of that a substrate 100 carrying a metal film is conveyed in a metal wet etching machine 10 when a LCD (Liquid Crystal Display) panel is manufactured. In the LCD panel manufacture, the metal wet etching machine 1 is used for executing a wet etching to the metal film. The metal wet etching is to load the substrate 100 which the surface is plated with the metal film (metal layer) in an etching bath full of acid solution. Then, etching is performed to the area unprotected by the photoresist to obtain the patterns protected by the photoresist. Before the metal wet etching machine 10 is used to perform etching to a batch of metal films. One of the batch of the metal films is selected as being a sample metal film and to acquire an etching end time of the sample metal film. Two ways of performing the etching end time detection exist in the industry nowadays. One is shown in FIG. 2, which shows a diagram of that a work 150 executes a random check for judging the etching end time of the metal films with unaided eye by experience according to prior art. However, this way is less precise because digitized management is unable to realize. The other is to acquire the etching end time of the sample metal film through the scanner 104 of the EPD (End Point Detector). The etching end time is defined as the period of time from loading the substrate 100 into the etching bath full of acid solution till the sensor of the end point detector detects the metal film penetrated by the light (the substrate 100 is used for carrying the metal film).
The working theory of the end point detector is based on the light reflection/penetration. As the metal film remains on the substrate 100, the light generated by the sensor of the end point detector is still reflected by the metal film because the light cannot penetrate the metal film. The end point detector judges that the end point time of the metal film has not arrived hereby; as the metal film carried by the substrate 100 is completely etched, the light generated by the sensor of the end point detector can penetrate the substrate 100 and is not be reflected because the light can penetrate the substrate 100. The end point detector judges that the end point time of the metal film has arrived hereby.
However, as shown in FIG. 3, considering the functions of the metal film on the substrate 100, functioning area 100a and dummy area 100b can be illustrated. The dummy areas 100b are the areas without patterns (without photoresist), and the patterns of the functioning areas 100a are divided into a great many tiny and irregular shaped areas when the exposure process is performed. Therefore, when the functioning areas 100a are etched with acid solution, the etching time is simply related with the thickness of the metal film; but the dummy areas 100b have no patterns and the entire area is relatively larger than the functioning areas 100a, when the dummy areas 100b are etched with acid solution, the etching happens from the exterior to the interior slower. The dummy areas 100b have the same thickness as the functioning areas 100a do but the needed etching time takes longer.
Although, the etching end time of each metal film can be detected with the way through the end point detector, the set up location for the scanner 104 affects the judgment of end point time directly because the end point detector according to prior art as shown in FIG. 4 utilizes a single point scanning manner. Generally, the set up location of the scanner 104 is a fixed position as performing scan. However, the distributions of the functioning areas 100a and the dummy areas 100b are different in the metal films of different substrates. If the fixed position of the scanner 104 makes the scan covers the dummy areas 100b most, it results in that the detected end point time can be longer than the really needed etching point time. Then, the error of the judgment of the end point time obviously becomes larger.
Consequently, there is a need to provide an end point detecting method of metal etching and device thereof for solving the existing drawbacks of aforementioned prior art.